Pedestrian traffic control signals are provided at many crosswalks of the busier street intersections in order to direct pedestrian traffic, and to reduce pedestrian accidents. The National Safety Council originally approved a type of pedestrian traffic control signal which is energized alternately to display the word Walk and the words DONT WALK. The present standards tend to adopt DONT WALK in Portland orange and WALK in lunar white.
The words WALK and DONT WALK are formed in the usual prior art type of pedestrian traffic signal by neon or other luminous gaseous tubes which are energized at relatively high voltage by transformers mounted within the casing of the individual signal. The usual prior art signal has presented problems, both from a maintenance standpoint in the replacement of the luminous gaseous tubes, and from the standpoint of short-circuiting due to corona effects as the high voltage leads within the case absorb moisture and create discharge paths to the casing wall.
An adapter unit is described in U.S. Pat. No. 3,873,969 which issued Mar. 25, 1975 in the names of the present inventors which may be readily fitted into the housing of existing pedestrian signals of the general type described above. The adapter unit described in the patent, in one embodiment, comprises a support bracket which fits over the transformers within the casing, and which is held in a press-fit within the casing so that there is no need for holes to be drilled, or for screws or bolts to be used in mounting the adapter unit of the patent.
The adapter unit disclosed in the patent also includes a socket support which is affixed to the bracket and which includes a plurality of electrical sockets mounted on the support. The high voltage windings of the transformers in the casing are connected by relatively short leads to the sockets, and these leads may be spaced at relatively large distances away from the walls of the casing so that there is no chance of corona effects occurring. In the adapter unit described in the patent, the neon tubes which illuminate the signal are mounted in an enclosed module which has electrodes extending out from its rear side, and which are received in the sockets supported in the casing, as described above.
The adapter unit of the present invention is somewhat simpler than the adapter unit described in the U.S. Pat. No. 3,873,969, in that the enclosed capsule containing the neon tubes is supported within the cover of the casing by two simple bars extending across the rear face of the capsule in spaced, parallel relationship, and which are clipped into appropriate brackets mounted in the cover at the top and bottom sides thereof. The electrodes which extend through the rear wall of the capsule, unlike the adapter unit described in the aforesaid patent, are directly connected to cables from the transformer. The cables are preferably enclosed in rubber sleeves, or tubes, to minimize corona effects.
The structure of the invention simplifies the installation of the adapter unit into the pedestrian traffic control signal, and it also eliminates the need for relatively long high voltage leads between the transformers in the signal casing and the neon tubes within the capsule, which leads are subject to moisture absorption and resulting corona effects. For servicing purposes, the cover of the signal is opened, the supporting cross bars are unclipped from their brackets, the high voltage leads are disconnected from the capsule, and the entire capsule is easily removed, and may be replaced by a new one. The capsule itself is enclosed by a front planar lens element on which the words DONT and WALK are inscribed.
The adapter unit of the invention is also advantageous in that the enclosed capsule may be conveniently shipped with a minimum incidence of breakage of the fragile neon tubes within the capsule. The capsule itself is rugged and strong, and is not susceptible to fracture.
A feature of the invention is that the adapter unit may be easily installed in existing pedestrian control signals with a minimum of effort, and with a minimum of expense. When so installed, the signal is easy to service, and is not susceptible to corona effects.